Lump On Forehead, Hard And Painless, Dermoid Cyst. What Is It?

My 2 year old son developed a pointed lump on his forehead - near his hairline and just to the front and above his temple. It was hard, painless, non-movable and the skin moved freely over it. The area around it felt "odd" (hard and slightly lumpy). Over the next 3 weeks or so, the shape and size of the original lump has changed and the area around it that originally felt "odd" has now become lumpy as well. The lumps are clustered. We have had him to three doctors so far and have been given a different "guess" each time. We were told it was perhaps scar tissue, perhaps a bump on the head, a dermoid cyst and today was told that it was for sure not a cyst - no skin is involved and that it is all bone - and should be biopsied. I'm concerned for many reasons - all of which should be easy to figure out. No MRI or CT scan has been done, no blood work or anything. A couple questions - are they taking us down the right path to figure out what this is and does anyone have any idea at all what may be going on with my little guy?