If it is the very first line, you can use a combination of wc (word count) and tail.
You would need a temp file. Echo your first line into it.
Use wc -l to count the number of lines in the original file.
Subtract one from that to get a #.
Use tail -n # >> tempfile to cat everything past the first line.
Then, replace the original with the tempfile.
Of course, somebody will prob'ly come up with a single line replacement command using sed or awk or something.