I agree with Gareth, don;t overdo the fiber but make sure you are getting enough for your weight/height.
It could be a hemmy or the fissure, since you didn't mention pain, it would be impossible to know without an exam, I would think.
Since you strained, I wouldn't worry. I still had occasional bleeding with hard stools/straining almost a year after my LIS. You still have a compromised spot. If it continues, Jo, go see your Dr. for an exam. But let pain be your guide for worrying, not an occasional episode of bleeding!
Take care!