Thank you for posting your question here, I will try to answer it to the best of my abilities.
It could very well be your xyphoid process, it may have gotten calcified and that is why you feel the lump. But that is only one explanation, it could very well be a hernia
or a tumor
Since your insurance company isnt letting you take a CT scan
, at least get an x ray
done, it may show us what we need to see, it's a bit of a long shot, CT would have been ideal, but since it cant be used ask for an xray at least. It is way cheaper, they shouldnt mind.
I hope this answered your question.