What should I do for painful recurrent aphthous ulcers? Any blood tests or other tests to see what is going on?

Find cause. Some folks "simply get" these. However, if there's several at once, it can warn of a low level of good neutrophil white cells. Other entities to rule in or out based on your history are behcet's, lupus, and crohn's. A variety of remedies, from changing your toothpaste to dissolving a cortisol tablet on the lesion, are all worth trying. The best pain relief is still viscous lidocaine. Good luck.