Strange pop during local anesthesia

[ikafk]

I just had a cavity filled yesterday and while the dentist was numbing my jaw there was this weird pop and a sharp pain. It felt like when you're getting a piercing and they go through the multiple layers of skin just with a lot more pain. He didn't say anything so I didn't either but after he was like "Did you feel a weird pop" "yes." "Did it hurt?" "Yes." "Huh, weird." And then left to let the numbing take effect. Barely managed to not have a full meltdown.
It's the next day and it just feels really sore and bruised though there isn't any visible bruising and I'm just really freaked out by what happened and the fact that he didn't know what happened.

 

[Gordon]

Just a guess, but I think the likely reason is that there have been a slightly less than perfectly sharp tip on the needle so instead of cutting through the mucosa cleanly it sort of forced its way through. These days the tips are cut by laser so they're super clean and sharp but given the billions that are made the odd less than perfect one might get through the system.