If the check engine light is blinking rhythmically, there is a problem the computer thinks may cause damage to your car. If you notice a blinking check engine light, you do not need to stop in the middle of the bridge and call a tow truck (like you would with an oil light), but you do need to stop driving as soon as practical. Whether the check engine light is solid or blinking, it’s a good idea to drive gently.
Wonder if this applies.
Maybe you rotated a cam slightly causing it to be off?