you really need to be seen and have this looked at. if it's not herpes but a bacterial infection, you'll need antibiotics to clear it up and it sounds like this is fairly extensive. Be seen monday and deal with it.
have you ever been tested for herpes to know your own status? Can you recall ever having had a cold sore yourself? Odds are you didn't contract whitlow from your cousins cold sore. has your partner ever been tested for herpes?
whitlow only sheds from the area of the lesions. If you didn't use that hand on your partner, it wasn't a risk.
if you are going to bother to use condoms, you need to use them properly or you are totally wasting your time and money. condoms need to go on when the clothing comes off and stay on the entire time until your partner withdraws ( which needs to be done before they lose their erection totally so the condom stays on ). Have you both had full std testing? do you have pregnancy prevention covered?
grace
Herpes whitlow is really painful and I would highly advise you being seen by your provider for a work up on if it was. Regardless of such your risk is from touching with the finger itself. As long as you have the area covered that has the sores you will not pass it along. Sexual contact that doesn't involve that finger unitl the skin has fully healed is not going to lead to transmission.