How to repair torn vinyl flooring
First off that appears to be cheap PVC (Vinyl) sheet, not linoleum (linoleum is a natural product made from flax seed).  And the term 'grout' may set someone on the wrong path helping you.

Your faceless home store will have a variety of vinyl sheet goods glues and seam sealers for this purpose.  The seam sealer is probably the best bet as it comes in the smallest sizes, and you need just a tiny amount.

Dry it out first.  Open the windows, and get some heavy objects to keep it flat while the glue out-gasses and dries.  Use saran wrap to protect the heavy objects.