Thanks for writing your query.
It would be helpful if give more details like :-
1. Whether it can be moved by your fingers?
2. Whether any liquid discharge oozes out from it?
3. Any dark spot or opening on the skin overlying the swelling?
After reading your post, it seems that the swelling or bump on your forehead appears to be a lipoma
Lipoma is benign collection of fat cells under the skin.
You should not feel concerned about it except for cosmetic reasons.
It can be excised surgically for cosmetic reasons.
I hope this is helpful to you.