Welcome to Justanswer! I am Dr Altman and happy to assist you both today!
I am glad to hear that she is still eating and there are no signs of burns in her mouth. First, rinsing her mouth out and monitoring overnight for any changes orally as far as possible ulcerations. As long as the battery was not ingested I would be feeding a bland diet for a few days as a precaution, white rice and boiled lean meat (chicken as an example) along with pepcid (famotidine) 0.25 mg/ pound every 12 hours x 3 days which is an over the counter antacid.
Since you did not see any redness in his mouth, I think she was fortunate enough to avoid a burn. The puppies I see with this problem have an obvious area of inflammation where contact occurred, and it is quite painful. They often have difficulty eating their regular food and are depressed.
I recommend monitoring the rest of the evening for lethargy, reduced appetite or difficulty eating. If you see any of these, I would have her seen at your regular veterinarian in the morning.
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