Should i be concerned by a 6mm mass on brain. it is in the right thalamus?

Neurosurgeon: I believe that a neurosurgeon is best qualified to answer your questions after an assessment of your symptoms, if any, & examination and after reviewing your MRI images.

Severity?: There could be multiple causes pathologically to account for your "mass", and secondary metastatic lesion could be considered. In other words, you require a full evaluation. Yes, neurosurgery needs to be involved, but an adult neurologist should be consulted, as this requires full evaluation to properly sort out.