I had 8cm dermoid cyst, but im pregnant, can i go operation after i gave birth im only in my 2nd month pregnancy?

Yes, can wait: Most dermoid cysts are benign and probably will not interfere with your pregnancy . However, some are malignant and you should consult with your obstetrician about the advisability of waiting until after delivery. If you wait, the cyst should be followed closely by ultrasound to assure that it is not growing rapidly. If not, perhaps you could have a c-section and have it removed at same time.