That doesn't sound like a typical URI (upper respiratory infection) to me, but it may be very early stage. We did have one pig that was caught very early that sounded "a little raspy" and our vet commented that he wasn't sure how the foster mom even noticed because he could just barely hear the beginning of the lung noise in him!
If I were taking my guinea pigs to the vet, I would expect them to spend a lot of time listening to the lungs, both the upper and lower parts (because they sound different depending on the types of infections). If he suspects an infection, he will probably prescribe you an antibiotic. Don't let them give you pills. You can pill a guinea pig, but it's exceedingly difficult, and there are plenty of liquid alternatives that are much easier to deal with. Also make sure that the antibiotic is safe!
Here are a list of dangerous antibiotics of guinea pigs:
Many of these are fine for rats to take because their digestive systems are different, so make sure to double check. It's common for vets not to know if they don't deal a lot with rabbits and guinea pigs, they're fairly unique in this.
When our pigs have URIs (especially if they're not serious) we tend to start with Bactrim, which is the brand name of trimethoprim sulfa. It's a very gentle drug, and typically doesn't cause the type of digestive upset that some of the stronger drugs will. If that doesn't work, we then typically try Baytril (Enrofloxacin), as it is stronger. However, it does cause some guinea pigs to have anorexia and stop eating. If this happens STOP THE ANTIBIOTIC. Be sure to have Critical Care (a feeding supplement) on hand OR be prepared to grind pellets into mush and syringe feed. Get a few oral syringes from the vet's office while you're there, or you can get them from most pharmacies for free if you ask nicely.