Normally, if there is an entry on line 25 on page 1 of the 1040 ("Health savings account deduction. Attach Form 8889") and there is no 8889 attached to your return, then the IRS will quickly send you a letter asking for you to send in the 8889.
If, however, there is no entry on line 25 of the 1040, but you did have contributions (reported on your W-2 in box 12 with code "W") or distributions (reported on the 1099-SA), then your distributions at least may have reported as taxable, which would be incorrect.
So, first, wait three or four weeks for the IRS letter asking for the 8889. If nothing arrives in that timeframe, then amend your tax return, adding the 8889.
I suggest doing it this way because the IRS letter may not ask you to amend the return, but only supply the 8889 and perhaps pages 1 and 2 of the 1040.
But, in any case, when you get the letter, do exactly what the letter instructs you to do.
So there is less of a reason for the IRS to send you that letter quickly - it won't be until they notice that you had a code W on your W-2 or notice that you were issued a 1099-SA, which might not be for months.
In either case, I think you should do the same thing (wait for the letter and then amend in 3-4 weeks); I am just thinking that it is less likely that you will get the letter.
You want to correct this one way or the other, BEFORE April 18th.