It does sound like it might be a new attack, but these things can be set off by infections and viruses so it would be a good idea to see his GP and get checked for a urinary tract infection (UTI) as well as anything else the GP thinks of. (UTIs can be asymptomatic, so get it checked even if your husband doesn’t think he’s got one!)
Do call the MS nurse on Monday anyway - get this episode “on the record” at least.
If it doesn’t improve soon and isn’t a psuedo-relapse brought on by an infection/virus, I would suggest speaking to the nurse or GP about getting some help with it: vertigo can respond to neurophysio and there are meds that can help. If your husband thinks it’s his eyes, then seeing an ophthalmologist may be helpful too, if only to rule this in/out.
In the meantime, lots of rest!