My guinea pigs

Welcome. How big is your cage? The size maybe contributing to the problem.

Ditto @scoottie. Nipping is normal and shouldn't be a reason to separate, IMO. You should only separate guinea pigs if blood is drawn or one cannot eat because of the other and is losing weight because of it. If your baby guinea pig is constantly bullying the older one then that may also be a reason to separate. However, like scoottie said, cage size could be the problem. The bigger the cage, the less likely guinea pigs will fight. Lack of cage space is one of the common reasons pigs fight and don't get along. See the main page of this site for cage size standards. There is a bunch of info on why guinea pigs need a lot of space and how much they need based on how many piggies there are.

Another thing that could help is making sure there is 2 of everything, especially 2 feeding areas as you said that's where the younger one nips the older one. Have 2 hideys, 2 water bottles, 2 food dishes, and 2 hay areas on opposite ends of the cage.

It's only the 2nd day. Most likely they are just trying to work out who will be the boss pig. Guinea pigs like to create a hierarchy, like a wolf pack. Nipping is one of the dominance behaviors guinea pigs display. All piggie pairs are different, some will always show dominance behaviors, and some will only do it in the beginning and calm down as they get older and more mature. Let them be guinea pigs and just give them time.

Thankyou for replying and the size of my guinea pig cage is 56in×28in×14in