Most eye injuries happen from hay pokes or accidental scratches. They are a fact of life with piggies.
The occasional scratch from a misjudged leg swipe (which is the equivalent of a little nudge to keep somebody away from you) can also happen, but please never separate piggies unless they have had a serious fight with deep bloody bites. Instead of helping, you just stress out both piggies and their bond unnecessarily.
Most aggression in guinea pigs is not caused by them, but by their owners, who keep unmatched boars in too small, unsuitable cages and have not the first idea how piggy society works. If piggies are well kept in a spacious accommodation and their owners have taken care to also take likes and dislikes into account (instead of opting for looks), then serious fights are RARE because piggies have mechanisms in place to avoid them, as long as one of them can move away out of reach. It is really as simple as that!
Ulceration (the film on the eye) is not uncommon. Eye injuries tend to deteriorate very quickly but they thankfully also very often heal quickly again if seen and treated promptly. You are not reporting any of the more potentially serious problems, so I would take a deep breath.
Make sure that you get the meds in regularly. What generally helps with the healing process of an injured and infected eyeball is plain artificial tear gel (more effective than plain tear drops) to keep the eye well hydrated during the healing process. You can apply it 3-6 times in 24 hours but you have to wait for at lease half an hour after putting any medication into the eye to make sure that it is properly absorbed.
Ask somebody else to hold your piggy while you gently pull down the lower lid and get any drops in.
If you are on your own, distract them with food or place your piggy on your knees, facing away from you with a bowl of its favourite veg, fresh grass etc. in front of its head. Wait until it is fully absorbed in stuffing itself and then slowly sneak in the drops or gel from the dead angle behind the head. Guinea pigs don't multitask, so you have a better chance. It may take a few attempts, especially at first while the eye is still painful and sore, but it usually becomes easier once the eye has started healing and your piggy is realising that you are actually helping.
