I have been told that you need to worry if you see blood in your stool, versus on your stool. If the blood is in your stool, you should get checked out. I know that after tearing my rectum from hard stool, I can still bleed afterwards when my stool softens. Sorry if this is tmi.
There are many possible causes of rectal bleeding. From your description it sounds like an anal fissure or haemorrhoids - but you are right to get it checked out.
For more possible causes/symptoms/treatments, type in rectal bleeding to google/yahoo etc and click on to one of the many sites.
regards
Morecambe