Nap time help??

So Miles is standing! In fact that is all he wants to do is pull himself up to a stand! So my perfect little napper has now turned into a holy terror at naptime, standing up and crying instead of sleeping. The last two days he has only had one nap because he cried during the morning nap and would not go down no matter if I nursed him, if I rocked him to sleep and then put him down or if I went in repeatedly and layed him back on his back. He would just stand up and cry. He has been crying now for a half hour and my heart is breaking but I don't know what to do. He is so over tired. He was fine when I first put him down--just sucking on his thumb, but after a few minutes he decided to get up and he's been crying ever since. Does anyone have a method that they used to get their child to sleep? Do I go in and lay him back down and will that eventually work? Do I just leave him alone and let him cry it out the whole time? I tried to put toys in there that he could play with but he hasn't wanted that? ANY advice would be helpful!