I have a white sore on the tip of my penis about a dime in size and is very sensitive to touch as well as forskin deformation around tip of penis. Why?

Possible infection. Generally any new bumps or sores on genital should be examined by a doctor. Pain usually indicates infection unless you had trauma to the area. You should have tests for std's: gonorrhea, chlamydia, syphillis, hiv. These tests are not painful and require either urine or blood, not a urethral swab. Another possibility is herpes. It is important to provide a complete sexual history to the doctor.