I had the same issue but my problem was I had 3 different compounds. Test P, Mast P,, Tren A
I injected each separately into different muscle groups to narrow down which one(s) were causing the pain and inflammation.
I can tell you the inflammation was so severe, that 1cc into each pec resulted in pretty awesome looking pecs. Yes, I injected into the pecs because the lingering pain was so severe my normal injection rotation couldn't be completed with the short esters and EOD injection.
I contacted the manufacturer and they stated they use MCT oil in all their products. I have used their products in the past (longer esters) and never had this problem.
After 4 weeks of this, I switched vendors for the TestP and MastP. The problem was solved. The original vendor's Tren A was pain/inflammation free. I can't say it was the MCT oil.
Next cycle, I will try using vendor #1 Test P and Mast P separately, combined with the products from vendor #2. Just to see if diluting it with a pain-free product can salvage the remaining bottles I have.