Hi, and thanks for your medical question on eHealth forum!
Well, actually nothing as such may happen. However, sex may not be comfortable as the pelvic muscles and vagina may still be sore. Also chances of infection are high as there will be some discharge from the vagina for a few weeks. Another possibility is that vaginal wall would be lax and may not be able to contact around the penis during intercourse. Hence most doctors advice a woman to wait for 6 weeks before resuming sex, as this gives a woman's body time to heal and tend to the baby. Hope this helps. Take care!