I have small crusty bumps on my scalp. I can pick them off by scrapping with finger or comb. What could it be?

You can. Usually seborrheic dermatitis or psoriasis. A dermatologist will help you. Meanwhile you can get 3% salicylic acid (T-Sal, others) shampoo. Apply a few drops of water to the crusts, then a drop of shampoo. Get in shower a few hours later and wash out. Tar shampoo is favored by many but smells of tar.