I petted one of my dog and not other one | Reaction

The verb pet is usually inflected petted in the past tense and as a past participle. This has been the case for as long as the word has been a verb (about 500 years). The uninflected form (e.g., he pet the cat) is fairly common in informal contexts, especially in the U.S., but it usually gives way to petted in edited writing. Pet is gaining ground, though, and there is some precedent for it in the uninflected verbs let, set, and bet, so it may someday gain broader acceptance. For now, petted remains the safer choice.

Examples
Here are examples of petted in texts spanning the last few centuries:

And indeed, some familiar Horses love to be so petted, and will by that means eat twice as much as they would do if they were left to themselves. [A New Treatise on the Diseases of Horses, William Gibson (1754)]

[S]he, provoked at the apparent indifference of her petted darling, positively declared he should come to her, or be sent out of the room. [The Decision: A Novel (1811)]

We agreed, without any more consultation, that we would both go, and that Dora was a little Impostor, who feigned to be rather unwell, because she liked to be petted. [David Copperfield, Charles Dickens (1849)]

The stately donkeys were much petted and patronized, not by children only, but by that class of sight-seer whom the French denominate badaud. [Atlantic Monthly (1890)]