What Could Cause Bump On The Scalp & Mild Eczema?

Recently, I have several skin issues. I just felt a tender bump on my scalp while washing my hair. About a year ago my dermatologist said I had mild melasma, psoriasis on scalp & little on my hips that went away. More recently I have developed white patches on my face by my forehead & cheek. The Dr, thinks that it is mild eczema. I was worried it was vitiligo but she said she doesn't think so but is possible. What can be causing all this havoc? I am a 33 yr old female. Pretty healthy. Vegetarian diet. I take multi vitamins & supplements & am active. What is this tender bump on my scalp?