Seeing new lines on your forehead all of a sudden can definitely be alarming, especially if they seemed to appear overnight. Based on your photo and description, these lines don't immediately look like permanent wrinkles. There are several possible explanations, and many of them are temporary. One possibility is that they're sleep lines. If you slept with pressure on your forehead or in an unusual position, temporary creases can form and may take several hours to fade. Dehydration or dry skin can also make these lines appear more noticeable. Another possibility is that you're becoming more aware of your normal forehead expression. The forehead is constantly moving throughout the day, and repeated muscle activity can make natural expression lines more visible, even in your early 20s. If the lines remain visible even when your forehead is completely relaxed, they may represent early static lines. The good news is that these are often very treatable. A consistent skincare routine that includes daily sunscreen, a moisturizer, and a nighttime retinoid (if appropriate for your skin) can help improve skin texture over time. If the lines are caused primarily by muscle movement, Botox is often very effective at softening them and helping prevent them from becoming deeper. Since you mentioned your height and weight, it's also worth noting that significant weight changes can affect the way the skin sits on the face, although they wouldn't typically cause forehead lines to appear overnight. If these marks truly appeared suddenly and don't improve after a few days, or if they're associated with swelling, pain, changes in sensation, or weakness of the face, they should be evaluated to rule out other causes. The reassuring part is that, based on what you've shared, these lines are much more likely to be related to skin creasing or normal facial movement than to a serious problem. Many people your age notice similar changes, and if they persist, there are effective options to soften their appearance while still maintaining a natural look.