I'm surprised the processor is letting itself get to 98C before shutting down. I would think that it would shut down sooner than that. But no. Take SAAIELLO's advice. The thermal limit of that CPU is somewhere between 62C and 72C (I'm giving a range because I don't know it off the top of my head and for CPUs, 62C is the lowest limit I have seen and 72 the highest.)
It's probably still ok. Hopefully it saved itself.
So clean dust.
reseat heatsink with new thermal paste. dont forget to clean the old stuff off with isopropyl alcohol and a lint free cloth
ensure there is airflow in your case.
boot up and report back your temps and hopefully they will be normal again