My income is social security and dividends. The ObamaCare subsidy needs to be repaid (salary $4000 too much). Can I make an IRA contribution to reduce income.

I am retired and have social security and dividernds  for income (no W2 or taxable wages).  I withdrew more than I should have from my IRA last year and the health care subsidy on my tax return needs to be repaid.  I want to know if I can make a contribution before April taxes (in 2018) to reduce my income.