wait it out it could just be friction irritation from intercourse but if it persists see your dr.
Red itchy vagina can be due to a number of causes. First of all it can be due to allergic reaction or contact dermatitis to your undergarments, sanitary napkins or tampons, soaps etc.There is no change in the colour or smell of discharge in this case.
Secondly, It can be due to STD’s like Chlamydia or thrush(red,sore,itchy vagina along with pain during sex and slight increase in the vaginal discharge may be present), Gonorrhea(Itchy, red, or swollen vagina and Pain during intercourse, urinating or abdominal pain may be present),Trichomoniasis(red, very itchy vagina along with greenish, frothy discharge is present) or Lichen sclerosis which is a non-infectious inflammatory skin disorder which affects the vulval and perianal skin(Symptoms include itchy, sore and inflamed vulval skin which cracks, causing additional pain and stinging and treated with a strong steroid cream).All of them except lichen planus can be transmitted after oral or vaginal unprotected sex.
I hope it helps. Take care and regards.