What should I do?? Please help! Horse maybe lame!!?

So I thought I noticed my horse resting his left back leg a lot today. (I just came home from vacation last night so idk what happened..i think it happened in the pasture) anyways.. he was acting kinda sluggish when I first got on him. Walking was ok but trotting him he seemed to drag his hoof a lil..I thought it was cause his hooves need trimmed..We cantered and he was fine, trot felt odd but his canter was good. Then I was trotting him on the left diagonal and it felt fine so I switched just to work on my right diagonal, i could hardly post to it at all and he started like limping in his left back leg. We went home and I put liniment on all four legs and wraped them with my quilt wraps that I have. What else should I do???