After intercourse, i found a crack under the foreskin, at the joint of glans and foreskin. it was with blood and pain. there was also redness of glans. is this due to some skin disease?

Not likely: It may just be traumatic sexual intercourse with mild bruising and skin irritation or tear.

Foreskin: Unless you have irregularities elsewhere on your skin, a skin disorder is less likely and more likely is that this is due to friction and/or reaction to a condom.

Skin issue: If none of what your described was present before the intercourse and appeared after, i would think that the intercourse caused it. I don't think of any sexually transmitted disease if you discovered it right after the intercourse. It sounds like an intercourse related trauma.