Red lump on corydora fin - Please help

[Mollyelzie]

Please I’ve checked my tank this morning and one of my Corydoras has a red lump on it’s fin I’m so worried please help me how do I help my poor fish. I tried my best to get a picture but my pictures are quite rubbish because he was swimming a lot. Please can someone tell me what this is I’m so worried

 

[Mollyelzie]

To add to my thread I went and picked up medicine straight away (interpret anti bacterial medicine ) it says it’s good for open sores and ulcers ect, praying that helps my fishies poor wound