Man, can't say I haven't been there
First, pop off the dust seal and spray aerosol cleaner in there to get it clean and dry. Just to make sure it's not just residue from the job. The dust seal won't hold oil. If it still leaks assuming they are a decent brand, I'd go with using a Sealmate, a strip of thin rigid vinyl, 35mm film, etc to clean whatever is stuck in there. If it still leaks, buy a different brand of seal do it again, and make SURE to do the plastic bag trick when installing over the sharp edges of the fork tube. That WILL ruin a new seal immediately.
Also, I like to put a very thin layer of RTV on the outside edge (against the tube) of the seal as a just-in-case-might-as-well.