Hi and welcome!
This is by no means good advice, just what I've noticed around here.
Usually, ulceration comes so fast and so suddenly that parents don't have time to post about it until after the fact. It's more likely that they come in and post things like, "OMG... it bled so much!!"
Usually, parents describe involution beginning with a gray spot in the middle that spreads.
I would *think* that your description sounds more like involution (the process that means the hemangioma is going away) than ulceration. But I'm the webmaster and not a doc.
If you can post a photo of it here, people will come in and give their opinions. Also, if you can send a photo to one of our experts, they are good at getting back to parents. http://birthmark.org/experts.php
If you can't post a photo here, email it as an attachment to email@example.com
and I'll take care of it. Often, photos are too large to post and no one knows how to shrink them down a bit.
But take a deep breath .... I think it's going to be OK.