My 10 year old gelding has a lump just above his hoof....please help me find a remedy.?

My 10 year old geldong was injured 7 months ago. He hit his foot on while on a gallop. It swelled and apparrently the sweeling harded. It looks like a hard lump just above the hoof. It somewhere on his right coronet. Please advice me if you know any remedies for it. i'd appreciate it so much.