He's injured so he is protecting himself. It's what animals do. They mask pain for as long as they can and defend themselves aggressively. Injured herd animals generally get pushed to the outside of the herd where they are more vulnerable.

Have caution, but give him some time to feel better. Once he gets regular turn out again, he should return to whatever he was before the abcess

"Keep an open mind so that your thinking can be flexible, but not much that your brains fall out."- self