Acting strange after grooming tail

by Joan
(Rome GA)

My shih tzu had chewed at the base of his tail until he was miserable and it was terribly matted. I used professional clippers and scissors to get the mat off. That was 4 days ago and he is acting very strange. He hides under the bed, which he has never done. When he comes out, he scampers with his tail pulled to the side and hurries to sit down. I figured his skin may be irritated, but now I am not sure what is going on. I read that he could have been dropped, which he wasn't or that his tail could have been dislocated, which it wasn't. Any ideas?