beginning of Jan I was diving with a mouthpiece which did not fit me, and I had big problems holding it/nearly got a cramp, but not sure if thats the reason of the problem.

A few days later I got pain and thought it is a wisdom teeth, which frequently grows a little bit (I am 36). Actually they all grow a bit wrong and the dentist told me already 15 years ago that they should be removed, but they told also my mother who is now 63 and the wisdom teeth are the only healthy teeth she has.....

On the beginning I couldn't open the mouth fully, later till almost now I couldn't close it 100 %.

After some time I thought it is the joint or muscle or something like that and not the teeth, and I got it because of the mouthpiece, also the pain has moved a bit, not not really in my mouth instead close to the ear.

Now even better than on the beginning it is now almost 1 month. Who shall I ask? A dentist, I don't think so, or?

Please advise.

Sounds like either pain from tooth (which can be referred to to other nerves on the face) or an inflammation of the temporomandibular joint (TMJ) or one of the facial nerves. Start with a dental check-up. If they don't find the source of the pain, then it probably is the second. Unless there is redness, swelling or fever, it is probably not an infectious process but rather just an inflammation of the joint/nerve for which the treatment is hot packs and anti-inflammatory drugs (like ibuprofen -- 200 mg 3-4 times a day but be sure to take with food). You can try that on your own or see a doctor who will probably tell you the same thing, up to you. If however it seems to be worsening or there is fever or obvious redness/swelling then go to a doctor straight away as there could be an infection.

Biting down on an ill fitting mouthpiece could have triggered the inflammation, but so could a tooth problem which is why a dentist should be the first stop.

Some people also get this as a result of grinding their teeth in their sleep, a dentist should be able to tell if you do that and, if so, can give you a night brace to wear.

Sounds like either pain from tooth (which can be referred to to other nerves on the face) or an inflammation of the temporomandibular joint (TMJ) or one of the facial nerves. Start with a dental check-up. If they don't find the source of the pain, then it probably is the second. Unless there is redness, swelling or fever, it is probably not an infectious process but rather just an inflammation of the joint/nerve for which the treatment is hot packs and anti-inflammatory drugs (like ibuprofen -- 200 mg 3-4 times a day but be sure to take with food). You can try that on your own or see a doctor who will probably tell you the same thing, up to you. If however it seems to be worsening or there is fever or obvious redness/swelling then go to a doctor straight away as there could be an infection.

Biting down on an ill fitting mouthpiece could have triggered the inflammation, but so could a tooth problem which is why a dentist should be the first stop.

Some people also get this as a result of grinding their teeth in their sleep, a dentist should be able to tell if you do that and, if so, can give you a night brace to wear.

I think it is the TMJ, I also developed a nice big Herpes (in my noise, as always), which in increase unpleasent feeling everywhere and a big infection on the back side of my head (just a hair not growing straight).

Do you have an idea how long an inflammation of TMJ usually lasts? Does a month sounds normal?

It depends on the cause. If it is due to a tooth problem it will continue and worsen until you get it taken care o

If it is due to grinding your teeth in your sleep, ditto although it may get a little beteter and then worse since tooth grinding can come and go.

If it is due to inflammation of the joint when you bit on the mouthpiece, it could last for many weeks but should be slowly improving and respond well to anti-inflamatory drugs and heat.

See a dentist.