I'm in the same spot! I need $3,000 more to fully fund my IRA for 2017 but still have 30K to pay off my student loans.
What I do every year is save my IRA/SL potential money in a savings account and use that to fund any gaps in my monthly SL payment goal and also take an automatic $200/monthly contribution to my IRA (which is why after 12 months I'm still $3,000 short). Then come the end of March, I make the decision to fund IRA or put toward SL.
I'm not going to be able to pay off my student loans this year but $3K could reduce payoff by 2 months. Comparing a 2 month reduction in payoff vs fully funding an IRA which I wont be able to do again for that year, it makes more sense to me to fund my IRA. Even though it just makes me more angry at those stupid student loans.
I think it depends on the person. I hate hate hate my SL but I try and remind myself that I have time to pay them off. I wont have the time to fund my IRA again for 2017 In your case, I would see how much earlier you could pay off your loans with that lump payment. If it's only a few months, you might lean more towards the IRA. Especially if you think you'll run into the same problem next year (meaning will you be able to fund IRA for 2018 with this aggressive payoff schedule?)
Also, consider refinancing your loan. I split mine between 2 lender who each offered a $500 sign up bonus. I got a lowe r rate and put and extra $1K to my loans. It helped me make the IRA decision. Good luch