Can/Should I change my Roth IRA contribution amount after filing?

Before filing, I thought I could contribute $3,000 to my Roth IRA this year. However in between filing and contributing to my Roth, I ran into some financial problems and ended up contributing only $2,000. How can I amend my taxes to reflect this change? Do I need to amend them since Roth IRA contributions don't affect my returns?

Thanks!