Dog limping very bad, please help?

I let my dog out and i dont remember him limping before i let him out to go potty, he stepped on a pile of dead grass, after that he layed down i wondered why, he was limping very very very badly, to now, which happend 2 hours ago, he is laying down nonstop, not getting his ball, not eating, not dirnking, looks very sad, this happend whenever he had a stomache ache, he doesnt feel good. i looked and theres a very sharp mulch chip sticking out of the ground, im guessing its that, but we looked very closely with a flashlight and theres no puncture wound, i put alot of pressure all over the pads, paw, thumb, nails, everywhere, he didnt yelp or pull away, i cant find where the pain is? please help what should i do? neosporin? pain killer? wrap it or just wait?