how to let him down easy

so i started my first job about a month ago and i became friends with this guy, personally myself i thought it was just friendly. He had been asking to meet me for about a week or so and i felt bad putting him down all the time so i agreed to meet him, one thing led to eachother and we ended up having sex. Afterwards he asked me “what we are” and i said that we could see how things go but i just don’t think i’m very interested. How can i put him down easily without making it awkward at work or between us in general.