My son is almost 7 months old and has started head butting the rails in his crib. is it safe to put bumpers on the crib?

No: Bumpers are not safe, especially at an age that your child should be rolling. Hitting the sides with his head is okay.

Normal/no: head butting is a normal transitional behavior in some infants.It is usually a self soothing activity like thumb sucking.They do not injure their head doing this.A 7mo can suffocate if the fall asleep next to a soft toy or bumper, so don't be tempted or tragedy may be the outcome.