Install tube sealant, Schrader?
To install the sealant you will need to remove the valve core. Insert the tool into the valve and unscrew the core.  Your sealant container may include one built into the cap of the container. My SLIME container came with one. You can purchase a valve core tool for a few dollars at an auto parts supplier or Harbor Freight. Deflate the tire, remove the core.  Follow the sealant manufacturers instruction in regards to amount of sealant, reinstall the core. Inflate the tire per the sealant makers direction.