Cane it's just a little dirty oil, just spin on the new filter and top up the level. It'll be fine ... bet you won't do it again. LOL
You only lose the oil in the filter, If you already started the bike the little bit of old oil is already circulated with the new. The other 5 new quarts will more than offset that little bit of old stuff, I wouldn't worry about it since you never really get all the old stuff out of an engine anyway.
**** happens to the best of us.