If that's white mucous from his nose, yes your rabbit needs to be checked. White nasal discharge is from a bacterial infection, which could be from a URI or possibly some foreign object like hay, that got stuck up the nose. The vet can take a look in the nose with an otoscope, to see if there's anything visible, then should prescribe the necessary meds.
https://rabbitwelfare.co.uk/rabbit-snuffles/
https://www.medirabbit.com/EN/Respiratory/Bacterial/URI.htm
https://wabbitwiki.com/wiki/Snuffles
Common ones initially prescribed for a URI are baytril, meloxicam, and bisolvon. Though in more serious cases, a culture may be taken and the appropriate antibiotic for that bacteria prescribed. Stubborn infections like pasteurella, may need a 'heavier duty' antibiotic like azithromycin.
There are risks with some antibiotics used with rabbits and some should only be given by injection and never orally, so just be aware and make sure you go to a knowledgeable rabbit vet. Baytil is one of the safer ones, but not always very effective.
https://wabbitwiki.com/wiki/Choosing_a_rabbit_veterinarian
https://rabbitwelfare.co.uk/recommended-rabbit-friendly-vets/
https://wabbitwiki.com/wiki/Veterinary_emergencies