Hi, I've had this with my pump cannulas recently. Every time I seemed to bleed. For me, and it might not be the same as everyone else, if after an hour or so bolusing insulin it still stings then I will change my site. I have experienced uneven insulin delivery in the past from these stinging/bleeding sites- bg unexpectedly high, or random very fast hypos.
I think the easiest thing is to try and move away from the area you hit whilst it heals up. I try and switch my cannula between my stomach and sides to give things time to heal.