Ignore it irl. Block and report them online. It's not worth getting upset over.
OP I'm sorry if they say this. But that probably makes them ugly people for judging you on your looks. Its not acceptable to pass such comments but people do it. Seriously, I would advice you to either shut them down there or ignore it. They clearly are immature.
I had a similar situation once I was in grade 8 and in recess time I was walking by note to self I'm actually a good looking fella 8/9 out of 10. This random girl says your ugly in front of my friends also I was very shy and insecure in gr 8 that hurt me a lot. But another thing happend was this girl I was talking to saw my pic and her friends saw it and said oh he's ugly and she msgs me oh all three of my friends call u ugly I got really cheesed but they could be jealous of you maybe those girls are just jealous or simply hoes for sure.