Problem with incisors-what to do?

One of my meeces is looking raggedy and is losing weight. He had been treated for ear crud, and has recovered from that pretty nicely. However he still looked very rough. I found a half eaten lump of kibble and a piece of dried bread, both foods which normally wold have been gobbled up immediately. On examination, it appears that one of his lower incisors is about 1/8 of an inch longer than the other. He started taking soft food when offered, and is looking better.

Is there any way I can clip that lower incisor? Or does that have to be done by a vet?