No, just a forefinger numbness would not be sign or symptom of MS. The following may be considered;
1) Pinched nerves in the neck can be responsible for this. A degenerative disc disease or bone spurs pressing on nerve twigs can produce the numbness. MRI of the neck can clinch the diagnosis. Read this resource;
2) Deficiency of vitamin B 12 can also be responsible for it. Getting a blood level of the vitamin B 12 would substantiate the diagnosis.
3) If you have a family history of diabetes and blood sugar has not been done for some time, you should get a diabetic profile to rule out the high blood sugar, which is again a possibility for the cause.
Please feel free for your follow up questions.