While it could be nothing, if the problem persists, you should certainly go get yourself checked with your local healthcare provider.
In particular, keep a vigilant eye out for such symptoms:
Abdominal cramps and/or pain
Rectal Bleed
Sudden weight loss
All could be signs of colorectal cancer and possibly even an ulcer or even a bleeding diverticuli. If it's truly in your "stomach" and not in some portion of your intestines, you might be a candidate for an upper endoscopy and possibly a Colonoscopy if you show any of the other signs.
Stay Healthy,
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