Go back to the start of your SSA-1099 & uncheck the box. You may have to follow the menus at the top to Wages & Income, say you'll go thru the topics yourself, then look for the retirement / SS section and reopen your SSA-1099.
The lump-sum section is intended to reduce taxes on large back payments of SS benefits (most commonly SSDI, not SSI which is non-taxable; rare with regular SS) by allocating the check to the years it was for, when your marginal tax rate was probably lower. It's not intended for regular monthly SS checks.
