Im 15 years old. Today I lifted weights then had dinner n after I tried to unknot my little brothers yo yo when I noticed that I couldnt move my thumb like I used to. I cant give a thumbs up, it s just the upper part of the thumb that cant bend upward. Theirs no pain just a weird,annoying and stressfull feeling when I try to bend it upwards and fail.

Does any 1 know whats wrong, how it could be treated (if possible) and if I should go to the doctors