What's a mum to do?

Am feeling a bit down. Nick has a bad mouth ulcer, a sty and a large lump under his arm. The Dr has just prescribed an antibiotic for Staphylococcus. Nick has been chewing his ulcer so his mouth is now a mess and his face is swelling up..... and there is not a damn thing I can do about it, as he doesn't understand the consequences of chewing the ulcer. Some days this whole autism thing is just so hard.