Swollen & reddish pectoral fin root/muscle

[TCMontium]

Today I realized that right pectoral fin root of my female apisto has some swollen pink meat with a curved red line. I don't know for how long she had that, but right now I can at least see that she doesn't use her right fin fully. So, it makes a disturbance for her.
She has some fry and the male is in the tank with them. Maybe male did it or stress caused it?
Can you identify the problem? What should I do? (first photo is her left side, it is healty)

 

[gerald]

I'd guess it's a bacterial infection; maybe something similar to these cases:
http://www.apistogramma.com/forum/t...-food-is-stuck-in-his-mouth.19766/#post-97930
http://www.apistogramma.com/forum/threads/a-borelli-tumour.20165/#post-98065