Should I block my FWB because he keeps pestering me and won't take no for an answer? (NSFW)

My god I'm trying so hard to be nice but he keeps pestering me to hookup even when I tell him I'm not available at certain times or days.I just had extended family over so beforehand I told him I couldn't chat for about a week. They just left and I started talking to him again and he sends me a dick pic while I'm playing with my niece. It's incredibly annoying because I told him I didn't want to receive those kinds of pics/messages.I told him I'm not available this week and he says he can't wait until next week.I was honest and told him my car is being used by family which he said that he can come pick me up.I told him that I can't just disappear and he tells me to sneak out when it's clear.These responses are buzz kills for me. It makes me not want to see him at all. I feel like an asshole but I honestly want to block him without any explanation at this point because he keeps sidestepping around my refusals.I don't dislike him...but when I can't come over... I can't come over! How hard is that to understand?