I know my coworker is flirting with me but I haven’t stopped it

So I 21(f) have a coworker 27(m) and he’s been flirting with me. I haven’t no feelings for him and I have a boyfriend. For some context my boyfriend is aware this coworker is flirting and is fine with it our relationship is complicated and we’re only together until we find someone else. Anyway this coworker likes me and i feel like I shouldn’t let him keep flirting since I have no desire to be with him but at the same time…the attention is nice. He’s a very attractive man and very sweet he’s just not really there emotionally and that’s something I really need in a partner. This coworker also is aware I have a boyfriend but he’s also aware of me and my boyfriend’s situation so I’m not sure if I should just let the flirting keep going or put a end to to not lead him on.