How To Treat Tenderness On Head Due To A Bruise?

Hello Doctor, I am a 30 year old female with some health issues. However my question for you today is why does it feel like I have a bruise on my head. This been going on for some time now and when I touch it, it feels tender and the same way a deep bruise feels. i have not hit my head or have no type of trauma that caused this so can you give me some insight of what this is, why this is happening and if it s dangerous? Thanks for your time.