Helmet to Helmet contact

[CT1]

The salient part of the above "cut & paste" is:

"While inadvertent contact between helmets may occur in close line play or as players are closely engaged, all involved must be aware when the proverbial “line has been crossed,” and an illegal act has occurred. When in doubt, it should be ruled a foul."

Your play seems to fall into the "inadvertent" category.