Hi, Welcome to ATD. Thanks for the query.
No need to be alarmed. It would form a small elevation, and slowly dissipate in sometime. Injecting air subcutaneously in the stomach region wont cause you any harm.
You don't need to do anything for it, it will usually subside by itself in an hour or so. You can try to press it, and if the hole made by the syringe is big enough the air might as well come out very slowly.
You will be ok. Don't worry. All the best.
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