The less healthy food shouldn’t cause any issues with your band – just your weight loss but the odd slip is ok.
It sounds like not following the 20+ rule may be the issue here. That could account for the central chest discomfort. Sometimes you can get a referred pain to your port too
Try not to worry. Go back onto liquids only then soft diet for a few days to allow any irritation to settle. Try sucking on some ice/ ice lollies too.
if things don’t improve, worsen or you have any concerns let your provider know.
The bands are hardy little things so hopefully the odd slip won’t have caused any longer term issues. Xx