7. If the child was born circumcised-Hatafas Dam Bris:[1]

If the child was born circumcised, without a foreskin, then one is to perform Hatafas Dam Bris, through puncturing the limb in a way that it releases some blood.

Examination and observation: This Hatafas Dam must be done very carefully, and is only to be done after properly examining with one’s hands and eyesight and after observation of several days to make sure that he does not have a foreskin has become stuck to his limb. This examination must take place even if the observation will extend past the eighth day, in order so he not be brought to danger.

Using metal: The examination may not be done using metal.[2] However, the actual removal of the blood may be done using metal and it is not necessary for one to use one’s nails to do so.[3]

Blessing:[4] A blessing is not recited prior to performing the Hatafas Dam, unless one can see a foreskin that is attached to the limb, even if he does not know for certain that it is the foreskin but it appears to be the case.

Shabbos:[5] This performance of Hatafas Dam may not be done on Shabbos unless one knows for certain that the limb contains a foreskin that is attached to it. However, if it only appears to be so but one does not know for certain that this is the case, then it may not be performed on Shabbos even though a blessing is to be said over the Hatafas Dam.

[1] Michaber Y.D. 263:4; See Pesakim Uteshuvos 263:6-7; See Encyclopedia Talmudit Vol. 9 Erech Hatafas Dam Bris p. 25

How to perform Hatafas Dam Bris: See Pesakim Uteshuvos 263:8 for the full details of this subject including where to puncture the penis and if actual blood must come out

[2] Michaber Y.D. 263:4 as explained in Taz 263:2

[3] Taz 263:2 in negation of Yeish Mefarshim

[4] Michaber 265:3; Shach 263:4; Tur 263; Bach 263

[5] Shach 263:4; Bach 263