Attic Space with locked off door-tenant is requesting access

[Fran Petrillo]

I have an attic space where my tenant is currently keeping his furniture. I originally wanted to keep it locked off but he kept asking for the space I eventually gave in :( however it’s not included in the lease. This attic space has a locked door and now my tenant is claiming that it is illegal to have it locked. I’m worried about potentially being sued and him not paying rent. Is my tenant within his rights to not pay rent? And what can I do about the locked door situation? I’m tempted to drywall it over. Also how to I get him to move his stuff out of the attic?