Not a Ben yomo
I accidentally fried chicken in the same oil, I used that pot for cheese
Can it be kashered?
If the chicken was fried when the pan was clean of dairy and aino ben yomo, it may be kashered with hagalah.
When meat is cooked in an eino ben yomo of dairy or vice versa, this is called “heteira bala” the taste absorbed is essentially kosher as before one was absorbed the other became “pagum” – unedible by sitting for 24 hours, and so hagala is sufficient.
See Biur Halachah 451:1, Shach Y:D 121:8.