Light spotting after sex 28 weeks

Hey ladies! So me & my husband did the deed this evening and I didn't pee until like 2 hours after (bad I know) but I just went to the restroom and when I wiped I had a small spot of bright red blood (about the size around of a pencil eraser) there wasn't any on my underwear and when I wiped 4 more times there wasn't any more. Should I be concerned? I haven't had any spotting at all my entire pregnancy so I'm a little alarmed