If as you say you have "serious" pain when you run, I would guess that might take a long time (if ever) to eliminate. Running is HARD on the body, and lots of runners have so much pain and chronic injuries that they have to switch to fitness walking permanently. The walking forums are full of injured ex-runners.
So, in my opinion if you are going to buy any bike you should perhaps concentrate on the road bike rather than a tri bike- you would be more sure to be able to use it for its purpose.