If its hurting, its trying to tell you something! Is there a physio locally you can get quick access to? I had a knee injury a couple of months before my first marathon in October last year, and had a fab physio who gave me some rehab exercises to do, but also helped me put together a cross training plan that would help me continue to develop my fitness and train whilst I rested the joint. And I still did better than I was expecting in the marathon. Better to take time to fix it now.
In the meantime, might be worth not doing the long run tomorrow and give the tendon a rest. Maybe cross train?
