Everything that is left on that pin is positive. The only difference between what you had before you broke it and now is that before you had a solid pin & now you have a pin with a hole in it (it looks more like a squonker now lol).
As long as the mod still reads your atty, you should be fine. In fact, it looks like that before it was broke the positive pin was wider. Now that you broke it, it is thinner, so there should be no way that it will short by contacting the negative 510 threads on your atty. However, if you do temp control, you may have a problem as it may not read well enough.
However, if it bothers you, then you only have 2 choices...
1) Throw the mod away
2) Find a 510 connector that is suitable for that mod and replace it. In the USA, FatDaddyVapes and Varitube sell 510 connectors. In china, Fasttech sells many 510 connectors. This, of course, entails opening the mod and doing some soldering (not much, but you do have to do some soldering).
Option 2 may not be worth it to you. I don't know. You will have to open it up, take many measurements and buy the 510 connector that is a best fit for the mods.