I have not come across any research showing that injecting near the injury site works better than injecting elsewhere. There are no large human trials, only a handful of rat wound-healing studies. For something with more actual evidence behind it, PRP injections are worth considering even though they are usually not covered by insurance and the procedure itself is quite painful.
I have had an Achilles tendon problem for five years that flares up with activity and leaves me in noticeable pain. That is why I started a daily BPC-157 and TB-500 combination at 500 mcg each, split morning and night, injected into the abdomen. After a month the combo eased several smaller issues but the Achilles remains swollen and painful, though slightly less than before. I have also followed a physical therapy plan and rested it more. The swelling sits right at the tendon attachment on the heel where there is almost no fat to inject into. Would raising the dose help, or should I try injecting close to the spot? I have seen claims that BPC works better when placed near the injury.