I have a sub-serous fibroid measuring (4.98 cmx 3.14 cm) in posterior left lateral wall of the uterus. Is it necessary to surgery right now?

No. Not unless pain, bleeding or a space related problem causing issues. At your age you may eventually need surgery but otherwise these are generally elective surgeries. Good luck.
Not emergency. Subserosal fibroids that are 4cm in size do not usually have to be removed. They do typically grow and sometimes require treatment (often including surgery) if they become large, grow rapidly, cause pain or interfere with your function.