Sliced watermelon

So, I recently learned eating sliced watermelon from a store is a NO NO because we can’t see how clean the cutting process is. I miss watermelon so much so I bought my own. I washed it and sliced it. I still feel weary about eating it even though I took all precautions to be clean. The watermelon was room temp/warm when I was cutting it which they say not to eat if it’s room temp. I’m just so confused. Advice?/ help?