This seems to be some trauma to your labia due to probably rough intercourse. It could be because of fungal infection
also. Do you have any curdy vaginal discharge? If so it is fungal infection.
If it fungal infection, you will have to apply antifungal medicines - not only to labia but also inside the vagina. Both of you will have to take this treatment simultaneously.
If it is not a fungal infection, some antibiotic cream locally will help you to heal the lesion.
You may require in all about a weeks treatment minimal.
Please get clinically examined from a Gynaecologist and get required prescription form him/her.
Till both of you are not completely cured, please observe total sexual abstinence.