Yes this can be normal around the time of implantation. Brown blood is old, so unless you start passing fresh, bright red blood you should be ok. However you should get attention if the pain gets worse or you pass clots.
Is Cramping And Brown Spotting Part Of Early Pregnancy?
Yes, It's normal to spotting during pregnancy in the early time. But you must visit the doctor to diagnosis your case for your better pregnancy stages.
You should concern about this. This can lead to abortion. Have a bed rest and consult doctor for hormonal support like HCG injections.