A couple of months ago one of our Welsummer hens was jumping up to the roost bar when several others were already bunched together with over 1/2 of the bar still open. She miscalculated and hit it hard. She had a big lump on her front thigh the next morning and discoloration from the bruising. She refused to put weight on it. When I checked her after it happened there was no signs of a break or damaged skin. She did make a ruckus and acted like it was broken, there was free movement of entire leg all the way to the pelvis.
I had to separate her into the dog crate with food and water within easy reach. She refused to walk, held leg up when she did stand. She was confined for 2 weeks and was able to walk within 3 days but would plop herself down. The end of the 2 weeks she was fine. She still has a slight limp but doesn't interfere with scratching or other chicken habits. She continued to lay eggs the entire time.
I looked over the roost bar thinking I may have had it too high, just over 3 1/2 feet from the floor, no rough edges, it is just a 2x4 wide side up. Plenty of room for them to spread out if they don't want to bunch together.
For her injury I think she just had a bad jump to hit the board making the big bump like your bird. So put her in a smaller space for a few days in sight of the others to see how she does. Less area to get to food and water less stress on her. Limited area to move around will give a better chance to heal the damage.
Good Luck!
