After an MRI in left hip, I diagnosed with a small amount of edema in the bone marrow and a likely enchondroma. Is it bone necrosis? What should I do?

An enchondroma. is a benign bone tumor. Unless it is very large, or in an area at risk for pathologic fracture, generally nothing needs to be done about it, except perhaps intermittent imaging follow up. The bone marrow edema is a nonspecific finding that could be due to a variety of causes. Talk to your doctor about it. It doesn't sound like there are any findings to suggest bone necrosis.