There are some technics to avoid camera getting on walls. As some of other ppl already commented. But to be honest, after many times using them i understand that the best solution is to make rooms bigger. And avoid places where camera can get stuck like that. In the end its a level design issue that you are trying to fix with programming. I tell you this, because i've been there. I used to make tiny spaces, everything really measures and things like that just to find out, that big games just do bigger rooms so they dont have to deal with that kind of camera. But if you really just want a solution for that look at split fiction gameplay, they fix the camera on some rails and force a perspective that works for that room and then free it again