Tweaked hamstring

I'm well into my training towards this year's Stockholm Marathon (June
9th) and on Sunday evening I ran 18 miles in 2.30mins which for me is
a pretty good time. I felt really fast and strong at the end and could
easily have gone further. On Monday I rested and on Tuesday I went to
the local running track to do some 400 metre sprints. On my 10th lap I
felt my hamstring tweak and stopped immediately, hoping that it would
come to nothing. I was so upset as this is the first time I've damaged
a muscle for 18 months. Wednesday I couldn't run - too painful. I left
it completely on Thursday and iced it and deep heated it as much as I
could. Friday I went for a short 15 minute jog and felt okay. Today
(Saturday) I got up and my leg felt good - an awareness that it was
not rquite right but no real pain. I tried to go for a slightly longer
slow jog but it tweaked again. Aagghh!!!

I think its only a tweak and not a strain or a tear but have you any
suggestions for speeding up the healing? I'm not going to run for
another 5 days and I might try some cycling instead. I'm almost 50
years old by the way and I recognise that sprinting is not an ideal
exercise for me any more.