First of all – dont worry. That is nothing serious and most every nipple pumper will experience that. When you pump your nipples for a very long time you will develop water blisters. You can spot them on the tip of the nipple or on the side. First they are small and look as if your nipple gets white spots. Then they will grow and eventually open up while you are still inside the nipple sucker. Then you will find some liquid dripping out of the nipple suckers when you take them off. Usually the liquid is clear. Those opened water blisters burn a little but they will heal quickly.
It’s best to stop pumping your nipples for one or two days. Put some (antibiotic) lotion on your nipples and give them a gentle rub. Water blisters are mostly happening when you start nipple pumping. Once your nipples are more trained after some months it will happen less and less. The best thing to do is to take breaks every 15 minutes and to massage your nipples. Use lubricant (vaseline) and don’t pump dry because this would make the skin break even easier. When I do my coaching I look for white spots after 15 minutes and adjust the pressure or stop for a while. Beginners have to be patient. But it is a good idea to pump regularly if not daily. Just take some breakes and avoid overpumping. Watch video how to avoid water blisters while pumping nipples.