Millwall manager Kenny Jackett said: "I didn't see the offence but I've seen my goalkeeper's jaw and eye and they don't look good. Some key decisions didn't go our way."
Leeds boss Simon Grayson said: "I will await the referee's report before deciding whether to take any action against Jermaine. I didn't see an elbow so I can't comment on it. I would need to see the video, but Jermaine was booked so the referee must have seen something."
A goal in each half by Beckford took his tally for the season to 23 and left Leeds just two points off the top six while delivering a blow to Millwall's hopes of automatic promotion.
Grayson added: "That's three home wins on the bounce and a clean sheet. It was a big game and a big test for us. Millwall showed their quality, but we matched them and were delighted with the win."