A cap for curable material dispensing containers prevents the material from curing after opening the dispensing nozzle. Thus, when mounted on a partially-dispensed container, the nozzle cap preserves flowable materials such as air-cured glues, sealants, caulks, etc. In particular, a deformable sealant in the cap remains pliant, conforming in and/or around the nozzle tip to create a seal. A retention member frictionally grips the nozzle to prevent inadvertent release of the cap, yet accommodates nozzle tips cut to varying lengths.