Eek! 1000 photos on phone!

I was editing photos in iPhoto on my iMac and tried to photostream only one photo from an event to my iPhone so I could post it on Instagram. When I hit "share - photostream" the entire Event populated my phone - almost 350 photos. I want to remove them from my phone, but not from iMac. I don't want any other photos already on my phone to be deleted. Is there a way to do this? When I try to turn off Photostream on the phone settings I am told that turning it off will remove all the streamed photos from my device. I don't want all of them to go - just the 350 which went there in error. Cany anybody help? Thanks!