Luckily you're not that far away from that magic number, and reaching a 620 may be easier than you think. There are still options with some FHA lenders even with a 615, but they are few and far between and will usually come at a price i.e. higher rate adjustments due to the "risk" of a 615 score. The best thing is to at least see if reaching a 620 is possible, because this will open up more options for you. Of course to truly give you direction on increasing your score, your mortgage professional or credit advisor would need to review your credit report. Our credit reporting agency has a nice interface called the "what if simulator", which allows us to create custom scenarios that show what the potential score change would be depending on certain actions you may take. Sometimes this is as easy as paying a few hundred dollars down on a credit card, correcting mistakes on your report, or deleting derogatory trades that may be hanging on longer than needed etc...
If these "quick fixes" do not apply to your situation, then the mere passage of time with proper guidance may be in order. Fortunately you are close enough, where this "passage of time" may be short enough to still get you in before the deadline in November.
Providing you this information and guidance costs me or you nothing, and can we can usually determine what you need to do on the initial call.
At the very least you will know whats ahead of you.
Be happy to help !
Good luck !!!!