Can a radial head fracture occur with a fall on a bent elbow with minimal pain and some bruising should I go to the doctors if it is, casting right?

Yes it can. It can happen that way, but is usually caused by a fall onto the outstretched hand. If you have point tenderness over the outer elbow, or pain in that area when you rotate your forearm, it is likely to be a radial head fracture. The treatment will depend on the x-ray findings, your age and other factors.
Questions. Something to consider. Does the injury bother you? Does tylenol (acetaminophen) or Ibuprofen treat the discomfort? If you are not satisfied with the answers you come up with you can visit an urgent care center to rule out a radial head fracture. Treatment most often is a simple cast or brace.