Something like can do the work:
awk -F\\t 'BEGIN {OFS=FS} {n=split($3,aa,",");for (i=1;i<=n;i++) {$3=aa[i]; printf "%s\
" $0 }}'
First tabulation delimiter need double escape
then split the 3th token and get the number of elements in splitted array
then replace 3th token in loop with splited elements and print