You should really speak to the nursing school
advisor to find out what your best course of action is. We can only speculate since we don't know their requirements. Chem lecture & lab at my school is completely separate, so if you fail lab, it doesn't affect your lecture grade. Just like your school, lecture is 3 credits and lab is 1 credit.
If you speak with your nursing advisor, ask if there's a possibility that you can repeat just the lab this summer or during the Fall concurrently with your nursing courses. If it's just a 1 credit lab, they may let you do this, since you've already been accepted. Again, it all depends on the program, so speaking with them is the key.
Do you know for an absolute certainty that you have failed lab? Or have a D? Is there any possibility you have a C? If you have a C, I wouldn't worry about it.
Good luck! I hope you can just re-take the lab over summer be done with it