If you got it from a good matching company I would call them and ask what to do. They probably would check it out and replace the bad cell if necessary (even if they charge you it's worth it if the rest of the cells are 100% ok - they should be able to tell you by running the cells on their equipment). For instance I have bought 2 packs from ProMatchRacing before and they treated me really well when I had an issue with a hot cell (which in my case I didn't know what happened but I think somehow got shorted on my carbon fiber chassis because after they checked it out and didn't find a problem, next time I ran it it was fine, no hot cell). You see if you over-discharge or under-discharge one cell versus the others it gets hotter. The heat builds pressure from vaporizing battery guts and thus the "psssshhhhhhhhhhhh" or POP.
If you don't have someone to go back to, you need to be really careful when using that pack and discharging and recharging it until you determine if the problem still remains. If you charge nice and slow (very low amps like 1-2) you might get a cell that was accidently shorted to re-equalize. I have had that happen where only 1 run or 1 charge cycle I get a hot cell... I watch it carefully and the next run/charge it is fine, and the pack is still ok but I have also had cheap sport packs get a hot cell that won't come back. If you discharge the pack (run it hard, or discharge at 20-30 amps) and it still keeps getting hot, the pack is no good for racing and might be unsafe to use. The venting is to relieve pressure, but there is always a small risk it might not vent properly and go boom I have known folks have batteries to blow up on them so be careful it really can and does happen. Hope this explaination helps some.