How to fix a crack in laminate countertop
There is a seam filler to hide a seam not sure if this will work well on a crack. The other thing I have used are solvents acetone and MEK. The problem with solvents is they can really make a mess (I have only tried a few times to use solvents acetone gave the best results but the seam filler gell did work the best for me. 

I have never hammered laminate. After fitting a pieces and pre-gluing, I use window blind slats they allow the pre glued sheet to be put in place then I pull the slat closest to a Seam and make sure it fits then pull the slats and use a roller to push the top down into the glue. The filler gell I have used is designed to seal but it comes in colors to match as the gel has a little volume I don’t know if it will work for a crack in the material but I would check it out. Acetone may help but I have not had results that looked as good as the filler /sealer made by the laminate manufacturer. If you use a solvent a syringe or eye dropper will help control the amount put a drop in the crack and it will run down the crack (I understand this is horizontal) don’t add two much or it will make a mess as I did in the past. 

Use a couple of small scraps to practice I got to where I could hide a seam but not as well as the filler that matched. Two much will pull the contact cement / glue up and that’s when it has to be redone.