Right Hamstring Pain

The other day, after completing a 25 mile bike and a 1600 meter swim, I went to stretch my quads by pulling my heel to my glut.  Immediately upon doing this, I cramped up in the middle of my rt hamstring.  Yesterday, I swam 1600 and then biked.  It was sore until the evening when it flared up more. Today, I ran 4.5 miles at a very easy pace.  Again, I felt fine until this evening. 

Could a cramp in the hamstring cause such continued pain, which now seems to be exacerbated by exercise?  I am using some leftover anti-inflammatory patches plus taking IBU.  Today, is the worst of the days. 

Do you think I could ride and swim tomorrow? I'm not sure if running or biking or both contributes to the pain.  I don't want to rest, but I certainly don't want to become injured. 

What do you recommend? Thanks!