Its quite normal when a comparative very big and thick penis goes inside vagina then there may be some itching. But all this will heal automatically. No need to worry.
it sounds like thrush to me.
I was told by my pharmacist that if you get a powderd form of a pro-biotic, you can apply it directly to the affected area so that it goes straight to work and sorts out the imbalance that might be there.
give it a try - if it does not work then you will need an antibotic.