Please a question answered about shot

[Phoebes (GA)]

When I gave phoebes insulin shot this was the first time I felt all the insulin go in then keep like a hard lump where it was at???!!!! What did I do wrong? I shot just over her left shoulder. But it left a bubble, a hard bubble

 

[Yong & Maury GA]

Edit: If you read previous, that was a human article.

This article says it can happen with vaccinations but it might still apply to insulin injections since we're still sticking a needle into them.

"The short answer is yes, a small (pea sized), mobile, firm, painless lump at the injection site can occur. This is caused by a "granuloma", which is a collection of immune cells. Most of the time, this lump will go away within a few weeks. Warm compresses can help to resolve these lumps."