Hi Doctor, There is a sudden formation of small hard lumps on forehead without any external injury. It is painful and also carries mild headache and eye stress. It occurs occasionally ( happened once last year, and next was today) and disappeared on it's own within 3 days  . We are concerned about what might be the cause and what is it exactly?Also,does it need to be treated ? It would be really greatful if you could give us some information regarding the same. Thank you.