Not a doctor, but it could be Hand Foot Mouth, its going around right now, lesions look very similar to early stages. If it gets worse, you may want to go to doc, if it is HFM, you will see more and more bumps and possibly on the bum. Sometimes in the mouth which appear as "canker sores" - but sometimes just a few like this. It goes away on its own after a while, but causes quite a bit of fever in the meantime. Hopefully it's a few bug bites, but keep an eye on it.