1998 GMC C1500 water

Hello
Thanks for the donation.

Did this occur after/during a rainy/snowy day? If so, check all weather stripping on doors and cowl area of front windshield.

It did rain all day yesterday then turned to snow last night, should I worry about this or get it fixed right away?

Eventually the water is going to cause mildew to set in the floor carpeting and of course rust can also form on the metal under the carpet. However, rusting is a process that takes a very long time so you shouldn't worry about this so long as you get the issue fixed before it rains too many more days on the vehicle. The mildew will set up rather quickly though, so drying up the water the best you can after every rainfall is important until you can get it fixed.