Poor little guy!
My colt was strong and stood up right away and he still had trouble finding the nipples on the mare. He would suck, suck, suck, all over her body and right between her hind legs, but she had had a lot of foals so her nipples hung low and he could never seem to find them. For about the first 24 hours I would help him get the nipple in his mouth when he was in the right vicinity, because otherwise he would suck as high as he could reach and never find the right spot. I actually tried a baby bottle too but he never got the hang of it. Luckily after a day or so of assistance he learned where the milk came from. I think it was about 4-5 hours before I actually got a good meal of colostrum into him.
I hope your little guy gets strong in no-time and can stand and nurse soon. Hugs and well-wishes!