Do you mean Lymphocystis? If so it is a viral infection that usually attacks fish when they are stressed. Although there is no known cure keeping your fish stress free will help the disease to run it's course. Keep water conditions good by providing him with and aquarium heater and regular water changes to keep ammonia and nitrite levels down. Fish with Lymphocystis are prone to secondary bacterial infections so keeping his tank clean through regular water changes will keep harmful bacteria levels low and help to prevent any secondary infections. I would keep Indian Almond leaf in his water because it prevents stress, has natural anti-bacterial properties and in general bettas love it so it would be very beneficial to your guy.
Don't give up, if your guy can make it through once the virus has run it's course he should be fine