What should I do if the blister on my nipple self burst/pop?

I really feel you on this, being a first-time mum dealing with nipple blisters is so stressful and painful. Since it has already burst, just keep the area as clean and dry as possible to avoid any infection, and watch out for any redness, swelling, or unusual discharge. I would strongly encourage you to bring this up with your PD or a lactation consultant as soon as you can, just to be safe and to make sure it heals well. You are doing great, hang in there.