I'm having continous itching on my scrotum and private part. when i scratch it i feel pain like little bruises.

Yeast: This is a common problem called "jock itch' or a yeast infection. Anti-fungal medications are used to treat this problem.

B 12 deficiency?: There are several possibilities. One possibility is that you have a vitamin b 12 deficiency, which can case the skin to itch. If you take b 12 use the sublingual under the tongue type for more absorption. Check w/your doc to make sure it is not something else.