I changed my tranny filter now the pan is leaking
Maybe, you may have bumped the gasket while installing pan, or maybe didn't tighten pan down evenly, or even overfilled the trans fluid. (trans fluid has to be checked at proper trans temperature.)
I would check it if fluid is leaking around pan. Do not tighten them down in one pass around the pan it has to be done in sessions. Only finger tight first time, second time just a half turn or so, third pass another 1/2 half turn or so tighter, you get the idea another pass until its tight but not so tight that the gasket moves out of place its rubber most likely.