Hi, my 22 month old boy has a bump, a small ball, on the left side of his neck. Could it be a lymph node?

Could be, or..... It depends on location, size, depth under the skin, changes in skin overlying bump and associated pain. How long has it been present?Is it soft or firm? Has he been ill or did he have an infection recently? A solitary enlarged lymph node is a bit concerning than the multiple enlarged nodes seen in many toddlers. Start with a check up by your pediatrician.
Probably. Reactive lymph nodes are extremely common in children and almost always are nothing to worry about. You can make a routine appointment with your child's pediatrician for an exam but an isolated enlarged node in a child without other significant symptoms is not an emergency.
Usually is. Lymph nodes are located throughout the body & generally noticable in exposed areas like the neck. They are usually pea sized at rest and enlarged when stimulated by bug bites, dermatitis, drainage or infection. They rarely can become damaged by infection & grow to golf ball size & need drainage or removal. Most enlarge and later shrink back down within a 3 wk cycle unless chronically stimulated.